Method, apparatus and computer program for digital transmission of messages

ABSTRACT

Embodiments relate to a controller operable to transmit digital data messages to a receiver via a communication link having at least a first and a second transmission path, the controller comprising a first signal terminal the first transmission path and a second signal terminal for the second transmission path. The first signal terminal is operable to digitally transmit a first message to the receiver according to a first transmission technique and the second signal terminal is being operable to digitally transmit a second message to the receiver according to a second, different transmission technique.

TECHNICAL FIELD

Embodiments relate to transmission of digital data messages to areceiver via a communication link.

BACKGROUND

Content or messages are transmitted in numerous applications. Forexample, Ethernet or related techniques are used to transfer a largeamount of data within the network of a company or via the internet. On asmaller scale, data is for example transmitted within vehicles, such asfor example within an automobile in order to operate power windows orthe like. Modern vehicles also utilize numerous sensors in order tomonitor environmental conditions, i.e. physical quantities related tothe operation of the vehicle or particular components thereof

Failure of the transmission of digital data messages between acontroller and a corresponding receiver via a communication link mayresult in a complete loss of the information intended to be transmitted.Moreover, in more complicated interrelated systems, a brokencommunication link may also result in the whole system becominginoperable or becoming inefficient. Therefore, there is a desire toincrease functional safety and reliability in the communication of datamessages.

SUMMARY

According to exemplary embodiments, a controller operable to transmitdigital data messages to a receiver via a communication link providingfor at least a first and a second transmission path comprises a firstsignal terminal for the first transmission path and a second signalterminal for the second transmission path. The first signal terminal isoperable to digitally transmit a first message to the receiver accordingto a first transmission technique while the second signal terminal isoperable to digitally transmit a second message to the receiveraccording to a second different transmission technique. That is, thecontroller sends, to the same receiver, messages using two differenttransmission techniques at the same time or in parallel, whereinparallel transmission may also include scenarios where the first andsecond messages are sent with a predetermined time difference or oneafter the other. This may serve to increase functional safety byintroducing redundancy into the transmission scheme. Functional safetymay even be increased to a higher extent as compared to an approachwhere two independent identical communication links are redundantlyused, since two different transmission techniques are utilized tocommunicate with the same receiver. For example, this may avoid thatsystematic errors cease transmission, which might occur at the same timein redundant systems relying on the same transmission technique.

According to exemplary embodiments, a content transmitted by the firstand the second messages by the different transmission techniques isidentical. This can serve to increase the reliability in that thecontent can still be transmitted or received to or by the receiver evenwhen one of the transmission techniques encounters an error.

According to exemplary embodiments utilizing a data bus comprising atleast a first bus line for the first transmission path and a second busline for the second transmission path, the first transmission techniqueuses a variation of a voltage on the bus or on a first signal terminalconnected to the bus in order to transmit the message while the secondtransmission technique uses a variation of a current on the second busline or on a second signal terminal connected to the same. This canincrease reliability of the transmission in scenarios, where externalinfluences may distort voltages and, to a lesser extent, currents orvice-versa.

According to exemplary embodiments, a controller is operable to be usedtogether with a data bus having at least a first bus line for digitallytransmitting a first message, a second bus line for providing areference potential and a third bus line for providing an operatingvoltage, that is in a system where the controller is powered by anoperating voltage from the receiver and via the bus. A first signalterminal of the controller is connectable to the first bus line andoperable to digitally transmit the first message according to the SPC(Short PWM Code) protocol, varying a voltage on the first signalterminal to transmit the message. A second signal terminal of thecontroller is connectable to the second bus line and operable todigitally transmit the second message to the receiver according to theSPC protocol, using a variation of a current on the second signalterminal to physically transmit the second message. A third terminal ofthe controller is connected to the third bus line providing theoperating voltage. This can allow integration of a controller fortransmitting data messages in a backwards-compatible manner into anexisting system based on the SPC protocol. The functional safety canoptionally be increased when the second transmission technique using avariation of a current is used. The same controller, however, can stillbe utilized with standard setups in already existing environments.

According to exemplary embodiments, a sensor system also comprises asensor operable to provide a sensor signal indicative of a physicalquantity sensed by said sensor, wherein the controller further comprisesa sensor input terminal coupled to the sensor. The received sensorsignal or the content provided by the sensor signal may then betransmitted via the two different transmission techniques. This can, inan inexpensive and efficient manner, increase the functional safety ofsystems relying on sensor data also in unfriendly environments, such as,for example, in automobiles.

Some embodiments comprise a digital control circuit installed within anapparatus for performing a transmission as illustrated above. Such adigital control circuit, e.g. a digital signal processor (DSP), needs tobe programmed accordingly. Hence, yet further embodiments also provide acomputer program having a program code for performing embodiments of themethod, when the computer program is executed on a computer or a digitalprocessor.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of apparatuses and/or methods will be described in thefollowing by way of example only, and with reference to the accompanyingfigures, in which:

FIG. 1 shows an exemplary embodiment of a controller and a correspondingreceiver capable of communicating together via a communication link.

FIG. 2 shows a further exemplary embodiment of a controller.

FIG. 3 shows an example for a sensor system incorporating an embodimentof a controller.

FIG. 4 shows an example of a sensor system incorporating an embodimentof a controller in a backwards-compatible manner.

FIG. 5 shows a schematic illustration of an exemplary embodiment of amethod for transmitting digital data messages.

FIG. 6 shows a schematic sketch of a further exemplary embodiment of amethod for transmitting digital data.

DETAILED DESCRIPTION

Various exemplary embodiments will now be described with reference tothe accompanying drawings. In the figures, the thicknesses of lines,layers and/or regions may be exaggerated for clarity. It should beunderstood, however, that there is no intent to limit furtherembodiments to the particular forms disclosed, but on the contrary,further embodiments are to cover all modifications, equivalents, andalternatives falling within the scope of the invention. Like numbersrefer to like or similar elements throughout the description of thefigures.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of furtherembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the exemplary embodiments belong.It will be further understood that terms, e.g., those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

FIG. 1 shows a schematic illustration of an exemplary embodiment of acontroller 2 for transmitting digital data messages to a receiver 4 viaa communication link 6, the communication link 6 having at least a firsttransmission path 6 a and a second transmission path 6 b. That is, thecommunication link 6 provides the possibility to transmit messages viatwo different transmission paths 6 a and 6 b. A communication link inthat sense can be understood to be any physical coupling between thecontroller 2 and the corresponding receiver 4 which allows digitaltransmission of data messages from the controller 2 to the receiver 4.For example, this can be a wired data bus having two, three or anyarbitrary larger number of bus lines in order to distribute or transmitcurrents or voltage pulses/levels or the like. Further examples for acommunication link are one or more fibers in order to transmit opticalsignals or an air interface, i.e. a wireless connection, where differentinterface techniques can be incorporated as independent transmissiontechniques. An example for a wireless transmission technique can be oneof the mobile communication systems or transceivers standardized by the3rd Generation Partnership Project (3GPP), as Global System for MobileCommunications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSMEDGE Radio Access Network (GERAN), Universal Terrestrial Radio AccessNetwork (UTRAN) or Evolved UTRAN (E-UTRAN), e.g. Universal MobileTelecommunication System (UMTS), Long Term Evolution (LTE) orLTE-Advanced (LTE-A), or mobile communication systems with differentstandards, e.g. Multistandard Radio (MSR), Worldwide Interoperabilityfor Microwave Access (WIMAX) IEEE 802.16 or Wireless Local Area Network(WLAN) IEEE 802.11, generally any system based on Time Division MultipleAccess (TDMA), Frequency Division Multiple Access (FDMA), Code DivisionMultiple Access (CDMA), Orthogonal Frequency Division Multiple Access(OFDMA), WirelessHART (IEC 6259) or any other technology with amultiplexing capable physical layer like Filter Bank Based Multicarrier(FBMC) systems. Of course, short range communication systems such asBluetooth or ZigBee also can be used.

Since different techniques rely on different modulation and transmissionschemes, they can be vulnerable to different kinds of distortions sothat, even when one transmission technique fails to accomplish atransmission of a digital data message, the same can still betransmitted by the second transmission technique. When using, forexample, a wired data bus having at least two bus lines, one bus linecan be used to digitally transmit a first message to the receiver usinga variation of a voltage on the bus line, while the second message canbe transmitted using a varying current on the second bus line.

In order to provide the signals for the transmission over the first andsecond transmission paths 6 a and 6 b, the controller 2 comprises afirst signal terminal 8 a for the first transmission path 6 a and asecond signal terminal 8 b for the second transmission path 6 b. Thatis, the signals used to transmit the digital messages according to thefirst transmission technique and the second transmission technique areprovided at the signal terminals 8 a and 8 b, respectively. Those can,for example, be directly connected to bus lines of a wired data bus orto antennas of a wireless communication system or the like.

According to one exemplary embodiment, content transmitted by the firstand the second messages via the first and the second transmission paths6 a and 6 b is identical so as to increase functional safety andreliability of the system since the content can still be received evenwhen one of the transmission paths is disturbed or broken.

According to some embodiments, an order of bits used for a digitaltransmission of the content is different within the first message andthe second message when the same content is transmitted by bothmessages. That is, the bit pattern to transmit the same content usingthe different transmission techniques can additionally be scrambled ormodified in a predetermined manner so as to still increase thereliability of the system. For example, the individual bits of thesecond message can be the inverse of the bits of the first message. Evenin the unlikely event that an error affects both transmission techniquesin parallel and at the same time, there is still a chance to recover thecontent when different parts of the content are affected.

According to some exemplary embodiments, the length of a first sequenceof bits used to transmit the content in the first message and of asecond sequence of bits used to transmit the identical content in thesecond message is identical, wherein the bit value of each bit at agiven position in the first sequence is the inverse of the bit value ofthe bit at the same position in the second sequence. That is, the firstmessage can be the bit-wise inverse of the second message, which canprovide for additional redundancies due to interrelated properties of aredundancy information such as, for example, a cyclic redundancy checkvalue (CRC) which can be computed and appended to the first and secondsequences of bits individually prior to their transmission.

According to some exemplary embodiments, at least one message of thegroup of the first message and the second message is transmitted using aserial transmission protocol using signals of varying width to representdigital content. To this end, a signal of varying width can beunderstood to be a pulse width modulated signal (PWM) where a digitalquantity is represented by a fraction of a predetermined pulse length inwhich the signal is transmitted with a characteristic corresponding toone logical state, while the signal is transmitted with anothercharacteristic corresponding to another logical state in the remainingtime of the predetermined pulse length. To this end, the predeterminedpulse length can be understood as a common clock time interval on whichthe protocol relies and which, therefore, should be available at thesender and at the receiver.

However, a signal of varying width shall generally be understood hereinas any transmitted pulse shape or pulse formation in which acharacteristic length or time can be varied so as to represent digitalcontent. For example, two signal pulses of similar or identical shapewhich are transmitted with a varying time difference are also understoodto be a signal of varying width. That is, the signal corresponds to thefirst pulse, the second pulse and the signal waveform between thepulses. The use of a transmission protocol using signals of varyingwidth to represent digital content can permit use of simple andinexpensive devices due to the simplicity of the representation, whichcan furthermore provide for a high robustness with respect to asuperposition of external noise signals and the like.

According to some exemplary embodiments, a common clock time intervalfor the transmission according to the serial transmission protocol issignaled from the controller to the receiver using a preamble to acontent of a transmitted message, wherein a time difference between twosignal pulses in the preamble corresponds to an integer multiple of thecommon clock time interval. That is, the common clock time interval isdefined by the transmitter and provided to the receiver. This canprovide an extremely high flexibility in systems design since thecontroller can collaborate with a wide range of receivers or chipsreceiving the transmitted messages due to the fact that the controllerdefines the clock cycles used within the protocol itself. Especially insensor systems, where the sensors and associated controllers aretypically provided with large structural sizes allowing for onlymoderate operating frequencies, this can permit combining sensors withnearly arbitrary receivers or control units having a receiver, withoutthe need to provide receivers tailored to one particular sensor. U.S.Patent Application Publication Nos. 2009/046773A1 and 2010/002821 A1disclose particular ways to use a preamble to provide a common clocktime interval from the controller to the receiver. These documents areincorporated herein by reference in their entireties, and the provisionof a common clock time interval as disclosed in those applications isexpressly defined as a part of a particular exemplary embodiment.

According to some exemplary embodiments, a digital quantity isrepresented by two consecutive signal pulses transmitted with a timedifference of a predetermined number of common clock time intervals, thepredetermined number being related to the digital quantity. For example,the predetermined number of common clock time intervals between the twosignal pulses directly equals a number to be transmitted using theserial transmission protocol. That is, if the number four is to betransmitted, the second signal pulse is sent four common clock timeintervals after the first signal pulse. Each sequence of two signalpulses (which is a signal of varying width) representing a number or isalso referred to as a nibble. With respect to one particular embodimentof a protocol to digitally transmit data using nibbles, reference isagain made to U.S. Patent Application Publication Nos. 2009/046773A1 and2010/002821 A1. The protocols described therein shall be understood tobe part of one particular exemplary embodiment.

According to some embodiments, the serial transmission protocolassociated with the first transmission technique is the SENT (SingleEdge Nibble Transmission, SAE J2716 standard) protocol or the SPCprotocol. According to further embodiments, only the second transmissiontechnique uses one of these two protocols. According to yet furtherembodiments, both transmission techniques rely on the SPC or the SENTprotocol or, more generally, on the same protocol. To this end, aprotocol shall be understood to be a rule with respect to how digitaldata is mapped into symbols or bit sequences or generally into quantizedinformation to be transmitted at a time by a transmission technique. Itis important to note that, while the protocol can be the same for thetransmission over both transmission paths, the transmission techniqueitself, i.e. the particular way the information is physicallytransmitted over the corresponding transmission medium, can bedifferent. For example, a transmission technique in that sense can beequal to the physical layer of a typical protocol stack, while the SPCor SENT protocol or the logical protocol as referred to herein, shall beassociated to one single or a combination of several higher layerprotocols of the protocol stack. In that sense, digitally transmittingcan be understood to prepare digital data for transmission according toone of those protocols, while the transmission via a physical layeritself according to a transmission technique can typically use analogsignals or quantities. Of course, other exemplary embodiments can usedifferent protocols, such as, for example, pulse width modulation (PWM),Peripheral Sensor Interface 5 (PSI5, as standardized and developedfurther by the PSIS organization, http://psi5.org), PeripheralAcceleration Sensor protocol (PAS3/PAS4), Distributed Systems Interface(DSI, as standardized and developed further by the DSI Consortium,http://www.dsiconsortium.org). The individual protocols can be used totransmit one of the first message and the second message individually orto transmit both messages using the same protocol. It is additionallynoted that arbitrary other protocols suitable to digitally transmitmessages can be used in further exemplary embodiments which expresslyalso includes any future developments of those protocols.

Hence, data of the same protocol can, for example, be transmitted by atransmission technique relying on or being implemented in the voltagedomain and, in parallel, by a second transmission technique relying onor being implemented in the current domain. That is, variations involtage of a voltage level or voltage pulses can be used to transmit thefirst message according to the first transmission technique via signalterminal 6 a, while, at the same time, variations of a current on thesecond signal terminal 6 b can be used to transmit the second messageaccording to the second transmission technique. This can be beneficialin that, for example, additional voltages can be induced in the buslines in the presence of a magnetic field, while the current-basedtransport technique can be fairly robust with respect to the presence ofmagnetic fields.

FIG. 2 shows a further exemplary embodiment of a controller 2, operableto transmit digital data messages to the receiver 4 via thecommunication link 6. The controller 2 of the embodiment illustrated inFIG. 2 additionally comprises a sensor input terminal 10 for receiving asensor input signal 12 which is indicative of a physical quantity sensedby a sensor. That is, the controller 2 illustrated in FIG. 2 is operableto be coupled to a sensor, such as to receive a sensor input signalindicative of a physical quantity sensed by a sensor and to transmitmessages containing information on the sensor input signal to thecorresponding receiver 4. This can, for example, be useful in automotiveapplications, where the sensor data serves to provide input to drivingassistant systems, which in return means that a loss of sensor data mayresult in failure of the system and hence in an injury of a driver. Toincrease the functional safety, the sensor input signal 12 is firstprocessed by a common part of a protocol stack in the controller 2.However, the transmission over the first and second transmission paths 6a and 6 b is ultimately performed by two different transmissiontechniques in order to provide for the required functional safety of thesystem. To this end, the protocol stack implement in the controller 2could be seen as a protocol stack having higher layers in common, while,at the same time, providing for two physical layer protocols orinterfaces.

According to two further exemplary embodiments of controllers or sensorsystems discussed with respect to FIGS. 3 and 4 in the following, thehigher layers of the protocol stack or the transmission protocol can bethe SPC-protocol, introduced to allow an efficient readout of sensordata in automotive applications via a simple three wired bus.

While SENT is a unidirectional communication standard where data from asensor is transmitted autonomously without any intervention of the datareceiving device, i.e. the receiver, SPC provides for the possibility ofa half-duplex synchronous communication, where the receiver triggers atransmission. Generally, in SENT and SPC, a signal is transmitted fromthe controller or the sensor by a series of pulses, where the distancebetween consecutive falling edges of the associated pulses defines thetransmitted data words. That is, the number of consecutive clock cycles(e.g. three microseconds) between two consecutive pulses corresponds tothe transmitted symbol or data directly.

FIG. 3 shows an exemplary embodiment of a sensor system comprising acontroller 2 and a magnetic-field sensor 14 as well as a temperaturesensor 16. The controller 2, i.e. the sensor system of FIG. 3 isimplemented to be compatible with a standard SPC-application, as it canbe used in automotive applications to read out data of sensors. Whilethe application in FIG. 3 shows a combination of a magnetic field sensor14 and a temperature sensor 16 to be read out or to be controlled by thecontroller 2, further embodiments, of course, can also utilize differentsensor types to sense or monitor different physical quantities. Forexample, a physical quantity sensed by a sensor can be a voltage, acurrent, a resistance, a pressure, a force, a position/location, astrain, a magnetic or electric field or the like. According to theembodiment illustrated in FIG. 3, the controller 2 comprises a first anda second sensor input terminal 18 a and 18 b, having connected theretothe sensors 14 and 16. In the particular embodiments of FIGS. 3 and 4,the sensor input signals are already converted from analog to digital soas to represent the physical quantity as sensed by the individual sensorby a digital representation or number. According to further embodiments,however, sensor-raw data can also be provided to the sensor inputterminal, so as, for example, voltages or currents derived by theindividual sensor elements directly. In those embodiments, theconversion of the sensor-raw data or signal into a digitalrepresentation can also be performed by the controller 2 iself.

As the controller 2 of FIGS. 3 and 4 is designed to be operable withSPC-compliant receivers, the controller comprises three signalterminals, a first signal terminal 20 for a first transmission path, asecond signal terminal 22 for the provision of ground or, moregenerally, of a reference potential and a third signal terminal 24 forthe provision of an operating voltage powering the controller and theassociated sensors.

In this particular embodiment, the controller 2 comprises a digitalsignal processor (DSP) 26 having stored its associated program logic inread-only memory (ROM) 28, and having access to further data stored inan erasable EPROM (EEPROM) 30. While the read-only memory comprises datarequired for the operation of the DSP 26 itself, the EEPROM 30 can, forexample, comprise additional data, such as, for example, calibrationdata for the sensors associated with the controller 2, serial numbers,manufacturer codes or the like.

The controller 2, in particular the DSP 26, receives, via the sensorinput terminals 18 a and 18 b, sensor input signals indicative of thephysical quantities sensed by the individual sensors.

The DSP 26 then provides a first and a second message, comprisinginformation on at least one of the sensor signals of the sensors 14 or16. That is, a representation of the content provided by the sensors 14and 16, that is of the sensor signals, is transformed to appropriatemessages or to an appropriate message format. The message, that is thedigital representation of the content, is then transferred to an SPCprotocol generator 32 which transfers the message into the transmissionformat as required by the SPC standard. The protocol generator 32provides the message as ready for transmission according to the SPCprotocol to a first transmitter 34 or output stage operating accordingto a first transmission technique, and, in parallel, to a secondtransmitter 36 or current modulator, operating according to a second,different transmission technique. In the particular example, the firsttransmitter operates in the voltage domain, i.e., the transmissiontechnique relies on the variation of voltage levels on the bus lineconnected to the first terminal 20, as described in the specification ofthe SPC protocol. To this end, different voltage levels can be definedand the transition from one voltage level to the other voltage levelindicates the start of a time measurement according to the SPC protocol.

In parallel, the second message is processed by the second transmitter36, which is operating in the current domain. That is, the physicallayer implementation differs from that of the first transmitter 34 inthat the transitions between the different states of the SPC protocolare signaled by differing current levels. To this end, for example, acurrent level representing a logical “low” state can be defined to beone half of a current level associated to the logical “high” state.However, further embodiments may, of course, define other voltage and/orcurrent levels to transmit or signal the transition between thedifferent states.

In utilizing an embodiment of a controller 2 as illustrated in FIG. 3,one can use a standard, three wired SPC-bus and a corresponding receiverto read out or gather information from the sensors 14 and 16 associatedto the controller 2. Furthermore, the functional safety can be enhancedsignificantly in that the second transmitter 36 operates in parallel tothe first transmitter 34, so as to be able to receive the requiredinformation on the sensor signals even if one of the transmission pathsassociated to the terminals 20 and 22 fails.

This can increase the functional safety without having to implement twocompletely separate sensor and transmitter systems, each making use ofthe same technology. Embodiments therefore can be not only cheaper thansuch an approach but also be safer with respect to critical operatingconditions and environments. As already previously indicated, systematicerrors in two identical implementations can be avoided when implementingsystems according to which two transmission paths are used withdifferent transmission techniques in order to transmit messages to thesame receiver.

Although FIG. 3 illustrates an embodiment where the content of the firstand second messages is identical, i.e., containing identical informationabout the sensor signals, further embodiments be also send differentcontent by different messages via the different transmission paths.

FIG. 4 shows a further exemplary embodiment which is, partly, identicalto the embodiment discussed with respect to FIG. 3. Therefore, only theadditional components differing from the implementation of FIG. 3 willbe discussed shortly. While the first and second transmitters 34 and 36still operate in the current and the voltage domain, the embodiment ofFIG. 4 provides for the possibility of transmitting either separatemessages or further enhancing the robustness of the system by scramblingthe message before submission of the same in order, for example, toavoid burst errors or the like. To this end, the embodiment of FIG. 4additionally comprises a second protocol generator 38, which can beoperated autonomously from the protocol generator 32 providing theSPC-protocol. The second protocol generator 38 can also implement theSPC protocol. According to further embodiments, however, the secondprotocol generator 38 can also provide for another protocol capable ofbeing submitted in the current domain, as for example a Manchester-codedprotocol.

Irrespective of whether the protocols used in the protocol generators 32and 38 are identical or not, the embodiment of FIG. 4 provides for thepossibility of scrambling the messages prior to the submission to avoidadditional errors. The embodiment of FIG. 4 furthermore provides for thepossibility of activating or deactivating each of the protocolgenerators 32 and 38 independently. That is, the controller 2 of FIG. 4is operable to selectively work in a first operating mode using only thefirst transmission technique (the first transmitter 34) or in a secondoperating mode using only the second transmission technique (the secondtransmitter 36). To this end, a first Schmitt-trigger 40 is connectedwith its input to the first signal terminal 20 and with its output to asteering or control input of the protocol generator 32. A secondSchmitt-trigger 42 is connected with its input to the third signalterminal 24 and with its output to a control input of the secondprotocol generator 38. That is, when a voltage above a firstpredetermined threshold associated to the first Schmidt-trigger 40 isapplied to the first terminal 20 by the receiver or the control unitassociated to the controller 2, the first protocol generator 32 can beswitched in an operative state. Equivalently, upon occurrence of avoltage above a second predetermined threshold on the third signalterminal 24, the second protocol generator 38 can be put in anoperational state. To this end, a user of the controller 2 of the sensorsystem of FIG. 4 can configure the controller and the transmissiontechniques as to his specific needs, while the controller 2 does at thesame time provide backwards compatibility to standard SPCimplementations.

For the sake of completeness, FIGS. 5 and 6 illustrate schematicallyfurther exemplary embodiments of methods for transmitting digital datamessages. FIG. 5 illustrates an exemplary embodiment of a method fortransmitting digital data messages to a corresponding receiver via acommunication link having at least a first and a second transmissionpath. In an optional provision step 50, first and second messages to betransmitted are provided.

To this end, it can be noted that the first and second messages caneither be received from an external device, as for example illustratedin the embodiments of FIGS. 2 to 4 or, be created within the controlleritself.

In a transmission step 52 the first message is digitally transmitted tothe receiver via the first transmission path according to a firsttransmission technique. Furthermore, the transmission step comprisesdigitally transmitting the second message to the same receiver via thesecond transmission path according to a second transmission technique,the second transmission technique being different from the firsttransmission technique. Both transmissions may be performed in parallelor at the same time.

FIG. 6 schematically illustrates a further exemplary embodiment of amethod for transmitting digital data to a corresponding receiver,according to which the same content is transmitted via two messages inorder to provide for a redundancy increasing the functional safety of asystem, as e.g. employed in automotive applications.

In a message creation step 54, a content to be transmitted is processedso that a first message is provided such that the first messagecomprises the content and a second message is provided such that alsothe second message comprises the content. Comprising the content in thisrespect means that the identical content can be reconstructed fromeither one of the messages according to a reconstruction rule. That is,both messages, when transmitted, transport the same information.

In a transmission step 56, the first message is transmitted according tothe first transmission technique while the second message is transmittedaccording to the second transmission technique so as to allow for aredundant transmission and a possible reconstruction of the content evenwhen one of the transmission techniques fails.

While exemplary embodiments have previously been described in particularwith respect to sensor implementations, that is, for implementationswhere sensor data or sensor information is read out and transmitted by acontroller, further embodiments can also utilize the concept describedherein in other applications. For example, apart from automotiveapplications, functional safety can play a role in applications in theaircraft or space industry or the like. According to the previousconsiderations, the embodiments described herein or further alternativeembodiments can, therefore, also be applied in other technical fieldsand areas, such as for example the aerospace industry.

The description and drawings merely illustrate the principles of theinvention. It will thus be appreciated that those skilled in the artwill be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of theinvention and are included within its spirit and scope. Furthermore, allexamples recited herein are principally intended expressly to be onlyfor pedagogical purposes to aid the reader in understanding theprinciples of the invention and the concepts contributed by theinventor(s) to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the invention, as well as specific examples thereof, areintended to encompass equivalents thereof

Functional blocks denoted herein as “means for . . . ” (performing acertain function) shall be understood as functional blocks comprisingcircuitry that is adapted for performing a certain function,respectively. Hence, a “means for s.th.” may as well be understood as a“means being adapted or suited for s.th.”. A means being adapted forperforming a certain function does, hence, not imply that such meansnecessarily is performing said function (at a given time instant).

Functions of various elements shown in the figures, including anyfunctional blocks labeled as “means,” “means for,” etc., may be providedthrough the use of dedicated hardware, such as “a processor,” “acontroller,” etc. as well as hardware capable of executing software inassociation with appropriate software. Moreover, any entity describedherein as “means,” may correspond to or be implemented as “one or moremodules,” “one or more devices,” “one or more units,” etc. When providedby a processor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. Moreover, explicit use of theterm “processor” or “controller” should not be construed to referexclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, network processor, application specific integrated circuit(ASIC), field programmable gate array (FPGA), read only memory (ROM) forstoring software, random access memory (RAM), and non-volatile storage.Other hardware, conventional and/or custom, may also be included.

It should be appreciated by those skilled in the art that any blockdiagrams herein represent conceptual views of illustrative circuitryembodying the principles of the invention. Similarly, it will beappreciated that any flow charts, flow diagrams, state transitiondiagrams, pseudo code, and the like represent various processes whichmay be substantially represented in computer readable medium and soexecuted by a computer or processor, whether or not such computer orprocessor is explicitly shown.

Furthermore, the following claims are hereby incorporated into theDetailed Description, where each claim may stand on its own as aseparate embodiment. While each claim may stand on its own as a separateembodiment, it is to be noted that—although a dependent claim may referin the claims to a specific combination with one or more otherclaims—other embodiments may also include a combination of the dependentclaim with the subject matter of each other dependent claim. Suchcombinations are proposed herein unless it is stated that a specificcombination is not intended. Furthermore, it is intended to include alsofeatures of a claim to any other independent claim even if this claim isnot directly made dependent to the independent claim.

It is further to be noted that methods disclosed in the specification orin the claims may be implemented by a device having means for performingeach of the respective steps of these methods.

Further, it is to be understood that the disclosure of multiple steps orfunctions disclosed in the specification or claims may not be construedas to be within the specific order. Therefore, the disclosure ofmultiple steps or functions will not limit these to a particular orderunless such steps or functions are not interchangeable for technicalreasons. Furthermore, in some embodiments a single step may include ormay be broken into multiple sub steps. Such sub steps may be includedand part of the disclosure of this single step unless explicitlyexcluded.

1. A controller operable to transmit digital data messages to a receivervia a communication link having at least a first and a secondtransmission path, the controller comprising: a first signal terminalfor the first transmission path, the first signal terminal beingoperable to digitally transmit a first message to the receiver accordingto a first transmission technique; and a second signal terminal for thesecond transmission path, the second signal terminal being operable todigitally transmit a second message to the receiver according to asecond, different transmission technique.
 2. A controller according toclaim 1, wherein at least one message of the group of the first messageand the second message is transmitted using a serial transmissionprotocol using signals of varying width to represent digital content. 3.A controller according to claim 2, wherein a digital quantity isrepresented by two consecutive signal pulses transmitted with a timedifference of a predetermined number of common clock time intervals, thepredetermined number being related to the digital quantity.
 4. Acontroller according to claim 2, wherein a common clock time intervalfor the transmission according to the serial transmission protocol issignaled from the controller to the receiver using a preamble to acontent of a transmitted message, wherein a time difference between twosignal pulses in the preamble corresponds to an integer multiple of thecommon clock time interval.
 5. A controller according to claim 1,wherein a content transmitted by the first and the second messages isidentical.
 6. A controller according to claim 5, wherein an order ofbits used to transmit the content in the first message is different thanan order of bits used to transmit the identical content in the secondmessage.
 7. A controller according to claim 5, wherein the length of afirst sequence of bits used to transmit the content in the first messageand of a second sequence of bits used to transmit the identical contentin the second message is identical, wherein the bit value of each bit ata given position in the first sequence is the inverse of the bit valueof the bit at the same position in the second sequence.
 8. A controlleraccording to claim 1, wherein the communication link comprises a databus comprising at least a first bus line for the first transmission pathand a second bus line for the second transmission path.
 9. A controlleraccording to claim 8, wherein the first transmission technique uses avariation of a voltage on the first signal terminal to transmit thefirst message.
 10. A controller according to claim 8, wherein the secondtransmission technique uses a variation of a current on the secondsignal terminal to transmit the second message.
 11. A controlleraccording to claim 8, wherein the data bus comprises a third bus linefor supplying an operating voltage to a third signal terminal of thecontroller, and wherein the second bus line serves to provide areference potential for the operating voltage.
 12. A controlleraccording to claim 1, wherein the controller further comprises a sensorinput terminal for receiving a sensor input signal indicative of aphysical quantity sensed by a sensor.
 13. A controller according toclaim 2, wherein the digital serial transmission protocol corresponds tothe SPC (Short PWM Code) or the SENT (Single Edge Nibble Transmission)protocol.
 14. A controller according to claim 13, wherein both messagesof the group are transmitted according to the SPC or the SENT protocol.15. A controller according to claim 1, wherein the controller is furtheroperable to selectively work in a first operating mode using only thefirst transmission technique or in a second operating mode using onlythe second transmission technique.
 16. A controller according to claim15, wherein the controller is further operable to evaluate a signalcondition on the first and/or on the third terminal and to enter thefirst or the second operating mode upon occurrence of a predeterminedcondition on the first and/or the third terminal, respectively.
 17. Acontroller according to claim 16, wherein the predetermined condition isthe exceeding of a predetermined voltage level on the first terminaland/or on the third terminal, respectively.
 18. A controller operable totransmit digital data messages to a corresponding receiver via a databus having at least a first bus line for digitally transmitting a firstmessage, a second bus line for providing a reference potential and athird bus line for providing an operating voltage, the controllercomprising: a first signal terminal for the first bus line, the firstsignal terminal being operable to digitally transmit the first messageto the receiver according to the SPC protocol and a variation of avoltage on the first signal terminal to transmit the first message; asecond signal terminal for the second bus line, the second signalterminal being operable to digitally transmit a second message to thereceiver according to the SPC protocol; and a third signal terminal forthe third bus line, wherein the second message is transmitted using avariation of a current between the second signal terminal and the thirdsignal terminal.
 19. A controller according to claim 18, wherein thecontroller is further operable to selectively work in a first operatingmode using only the first transmission technique or in a secondoperating mode using only the second transmission technique.
 20. Acontroller according to claim 18, wherein the controller furthercomprises a sensor input terminal for receiving a sensor input signalindicative of a physical quantity sensed by a sensor.
 21. A sensorsystem, comprising: a sensor operable to provide a sensor signalindicative of a physical quantity sensed by said sensor; and acontroller operable to transmit digital data messages to a correspondingreceiver via a data bus having at least a first and a secondtransmission line, the controller comprising: a sensor input terminalcoupled to the sensor, the sensor input terminal being operable toreceive the sensor signal; a first signal terminal for the firsttransmission line, the first signal terminal being operable to digitallytransmit a first message to the receiver according to a firsttransmission technique, the first message comprising information on thesensor signal; and a second signal terminal for the second transmissionline, the second signal terminal being operable to digitally transmit asecond message to the receiver according to a second, differenttransmission technique, the second message comprising information on thesensor signal.
 22. A method for transmitting digital data messages to acorresponding receiver via a communication link having at least a firstand a second transmission path, the method comprising: digitallytransmitting a first message to the receiver via the first transmissionpath according to a first transmission technique; and digitallytransmitting a second message to the receiver via the secondtransmission path according to a second transmission technique, thesecond transmission technique being different from the firsttransmission technique.
 23. A method according to claim 19, whereintransmitting according to the first transmission technique comprisesvarying a voltage on a first signal terminal associated with the firsttransmission path; wherein transmitting according to the secondtransmission technique comprises varying a current on a second signalterminal associated with the second transmission path; and wherein thefirst message is transmitted according to the SPC or the SENT protocol.24. A method according to claim 22, further comprising: receiving acontent to be transmitted; and providing the first message such that thefirst message comprises the content; and providing the second messagesuch that the second message comprises the content.
 25. A computerprogram having a program code for performing a method for transmittingdigital data messages to a corresponding receiver via a communicationlink having at least a first and a second transmission path when thecomputer program is executed on a computer or processor, the methodcomprising: digitally transmitting a first message to the receiver viathe first transmission path according to a first transmission technique;and digitally transmitting a second message to the receiver via thesecond transmission path according to a second transmission technique,the second transmission technique being different from the firsttransmission technique.